Instant messaging (IM) provides near-synchronous, typically one-on-one communication between users of computers linked over a network. IM systems typically conform to a client-server model in which a server (or cluster of servers) is maintained by an IM service provider controlling traffic coming to and from the server. A user who wishes to use the IM service generally registers with the service provider and downloads and runs an appropriate IM client application. Using the IM client, the user can connect to the IM server in order to send messages to and receive messages from another user running a compatible IM client application. IM systems typically provide information regarding the online presence of other, remotely-connected users with whom messaging is possible. If the second user is not running a compatible IM application and signed in to the same IM service, the two users cannot communicate by IM.
Most IM users are users of conventional general-purpose computing devices, such as personal computers (PCs). Other techniques for messaging have also become available for users of wireless mobile devices, such as mobile phones and PDAs. For example, Short Message Service (SMS) is a text message service for wireless telephony networks that can be used to send short messages between users. Richer IM-like services have been slower to develop for mobile devices, and there has generally been a lack of unity and seamless integration between messaging systems for mobile devices and standard IM systems associated mainly with PCs and the like. This has limited the degree and quality of communication between PC users and mobile device users.
Some mobile devices are configured to operate in accordance with Wireless Application Protocol (WAP) or similar technologies. WAP is an open protocol designed generally to enable access to information and services on the Internet for narrowband devices. A WAP gateway converts WAP requests from a WAP-capable device into HTTP requests and converts the information returned by a web server. A mobile device with a limited display may thus browse web pages written in Wireless Markup Language (WML). Other mobile devices may provide access to web-based or other Internet or Internet-like services by way of other protocols and technologies, such as iMode, or through HTML browsers running on the mobile device.